Very different parameter values produce similar results, making it difficult to understand the origin of these solar cycle properties. The solar cycle onset at mid-latitudes, the slow down of the sunspot drift toward the equator, the tail-like attachment and the overlap of successive cycles at the time of activity minimum are delicate issues in $\alpha\Omega$ dynamo wave and flux transport dynamo models. Finally, we determine that the difference in the mean magnetic field between the minimum preceding Cycle 23 and that following it is approximately 1G. This implies that the same near-surface magnetic perturbation is responsible. The size of the shift in oscillation frequencies between the two minima is dependent on the frequency of the oscillation and takes the same functional form as the frequency dependence observed when the frequencies at cycle maximum are compared with the cycle-minimum frequencies. This difference is statistically significant and may indicate that the Sun's global magnetic field was weaker in the minimum following Cycle 23. We use Global Oscillation Network Group (GONG) data to demonstrate that the frequencies of helioseismic oscillations are a sensitive probe of the Sun's magnetic field: The frequencies of the helioseismic oscillations were found to be systematically lower in the minimum following Cycle 23 than in the minimum preceding it. We perform an in-depth analysis of this minimum with helioseismology. That minimum is being followed by one of the smallest amplitude cycles in recent history. The solar-activity-cycle minimum observed between Cycles 23 and 24 is generally regarded as being unusually deep and long.
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